A hard-disk drive (HDD) is a non-volatile storage device that is housed in a protective enclosure and stores digitally encoded data on one or more circular disks having magnetic surfaces (a disk may also be referred to as a platter). When a HDD is in operation, each magnetic-recording disk is rapidly rotated by a spindle system. Data is read from and written to a magnetic-recording disk using a read/write head (hereinafter “head”), which is positioned over a specific location of a disk by an actuator.
A head uses a magnetic field to read data from and write data to the surface of a magnetic-recording disk. As a magnetic dipole field decreases rapidly with distance from a magnetic pole, the distance between a head and the surface of a magnetic-recording disk must be tightly controlled. An actuator relies on a suspension's force on the head to provide the proper distance between the head and the surface of the magnetic-recording disk while the magnetic-recording disk rotates. A head therefore is said to “fly” over the surface of the magnetic-recording disk.
Demand for increased HDD storage capacity has led to efforts to pack more bits onto disks. This increased density of bits, as well as increased rotational speed of the disks, requires highly accurate head tracking in order to minimize read/write errors. Advances in head gimbal assembly (HGA) have enabled smaller and lighter heads; however, these heads are subject to structural modes of the suspension; namely, the presence of high gain flexure modes which can cause head offtrack in Repeatable Runout (RRO) and Non-Repeatable Runout (NRRO). Adding support to HGAs in an effort to reduce and minimize amplitudes and coupling of these modes have negatively impacted pitch and roll stiffness values. Therefore, it is advantageous to minimize structural modes without requiring additional structural components or affecting separate dynamic characteristics of the HDD.